Pressure Deflection Research Articles

A pressure-deformation analytical model for rectangular diaphragm of MEMS pressure sensors

Rectangular diaphragm is commonly used as a pressure sensitive component in MEMS pressure sensors. Its deformation under applied pressure directly determines the performance of micro-devices, accurately acquiring the pressure–deflection relationship, therefore, plays a significant role in pressure sensor design. This paper analyzes the deflection of an isotropic rectangular diaphragm under combined effects of loads. The model is regarded as a clamped plate with full surface uniform load and partially uniform load applied on its opposite sides. The full surface uniform load stands for the external measured pressure. The partial load is used to approximate the opposite reaction of the silicon island which is planted on the diaphragm to amplify the deformation displacement, thus to improve the sensitivity of the pressure sensor. Superposition method is proposed to calculate the diaphragm deflections. This method considers separately the actions of loads applied on the simple supported plate and moments distributed on edges. Considering the boundary condition of all edges clamped, the moments are constructed to eliminate the boundary rotations caused by lateral load. The diaphragm’s deflection is computed by superposing deflections which produced by loads applied on the simple supported plate and moments distributed on edges. This method provides higher calculation accuracy than Galerkin variational method, and it is used to analyze the influence factors of the diaphragm’s deflection, includes aspect ratio, thickness and the applied force area of the diaphragm.

Modal analysis of a rolling truck tyre subjected to inflation pressure and vertical deflection

Modal analysis of a rolling truck tyre under inflation pressure and vertical deflection is conducted to determine its natural frequencies and mode shapes. A 3-D finite element model of a radial-ply truck tyre is used considering its multi-layered composite structure. The nonlinear effects of the inflation pressure, vertical load and rolling speed are incorporated in the analysis through an explicit dynamic simulation to determine the stress state throughout the tyre at instants when the modal characteristics are desired. The eigenvalues are subsequently extracted at three key moments when the tyre reaches the steady state after application of the inflation pressure, vertical deflection and rolling speed. For a deflected tyre, the conjugate mode frequencies, being identical for an inflated tyre, diverged to two different frequencies with one being lower and the other higher than the corresponding frequency of the tyre under inflation alone. The influences of the inflation pressure, vertical load and rolling speed on tyre natural frequencies are obtained through the development of a computationally efficient algorithm to automate the tyre model reformulations for parametric studies.

Non-linear buckling analysis of FGM toroidal shell segments filled inside by an elastic medium under external pressure loads including temperature effects

The analytical approach is presented to investigate non-linear buckling analysis and post-buckling behavior of FGM toroidal shell segments filled inside by an elastic medium under external pressure loads including temperature effects. The governing equations of non-linear buckling of FGM toroidal shell segments are derived based on the classical thin shell theory with the geometrical nonlinearity in von Karman–Donnell sense, Stein and McElman assumption and elastic medium modeled by Pasternak's two-parameter elastic foundation. The static critical buckling loads and the post-buckling pressure–deflection curves in two cases: movable and immovable boundary conditions including temperature effects are obtained by using the Galerkin's method. In the paper, the results are also compared with the solutions published in the literature for the specific cases. Effects of geometrical and material parameters, elastic foundation and temperature on the nonlinear buckling behavior of shells are shown in obtained results.

Effects of Synchronization during Noninvasive Intermittent Mandatory Ventilation in Preterm Infants with Respiratory Distress Syndrome Immediately after Extubation

Background: Noninvasive ventilation is increasingly used in very-low-birth-weight infants (VLBWI) to reduce complications that occur with invasive ventilation. However, the physiological effects of synchronization during noninvasive nasal intermittent mandatory ventilation (IMV) have not been tested in VLBWI immediately after extubation. Objective: We aimed to study the short-term effects of synchronized nasal IMV (S-NIMV) compared to nonsynchronized nasal IMV (NIMV) on breathing effort as measured by phasic esophageal pressure (Pe) deflection, spontaneous respiratory rate (RR), gas exchange, cerebral tissue oxygen saturation (StO₂) and intermittent episodes of bradycardia or hypoxemia in VLBWI recovering from respiratory distress syndrome (RDS). Methods: Fourteen VLBWI recovering from RDS were studied using a randomized cross-over design during both S-NIMV and NIMV (of 2 h each) immediately after extubation. Results: Phasic Pe deflection, spontaneous RR and transcutaneous PCO₂ decreased significantly while transcutaneous PO₂ and synchrony rate (defined as peak ventilator pressure delivered within the first half of spontaneous inspiration) increased significantly during S-NIMV compared to during NIMV. There was no difference in blood pressure, average arterial oxygen saturation (SpO₂), cerebral StO₂, fractional tissue oxygen extraction of the brain and severe bradycardia (defined as time with a heart rate <100 beats/min lasting ≥10 s) and in hypoxemic episodes (SpO₂ <80%) between the two modes. Conclusion: Synchronization during nasal ventilation immediately after extubation in VLBWI recovering from RDS improved gas exchange and decreased the respiratory effort, and it could therefore be considered to provide a more efficient respiratory support and synchrony.

Visual biofeedback exercises for improving body balance control after anterior cruciate ligament reconstruction.

[Purpose] To evaluate the effects of balance training after arthroscopic anterior cruciate ligament reconstruction. [Subjects and Methods] Sixteen patients (mean 33 ± 8 years old) who underwent anterior cruciate ligament reconstruction three months prior to participating in a one-month rehabilitation program. The control group included 15 people aged 34 ± 4 years. Patients’ functional level was evaluated according to the Lysholm knee score, and balance quality was ascertained by static and dynamic tests. A balance platform was used to measure the center of foot pressure deflection. Two dynamic balance tests evaluated time of task execution. [Results] Lysholm knee score improved significantly after rehabilitation. Balance in the sagittal plane with eyes closed improved significantly after rehabilitation. The average velocity of center of foot pressure swing in both the frontal and sagittal planes with eyes closed differed significantly from those of controls. Execution time required for the two dynamic tests decreased significantly after rehabilitation and were significantly better than those in the controls. [Conclusion] Maintaining static balance with eyes closed is very challenging after anterior cruciate ligament reconstruction. Maintaining balance in the sagittal plane is particularly difficult. A one-month rehabilitation program partially improves static and dynamic balance.

Heart–lung interactions during neurally adjusted ventilatory assist

IntroductionAssist in unison to the patient’s inspiratory neural effort and feedback-controlled limitation of lung distension with neurally adjusted ventilatory assist (NAVA) may reduce the negative effects of mechanical ventilation on right ventricular function.MethodsHeart–lung interaction was evaluated in 10 intubated patients with impaired cardiac function using esophageal balloons, pulmonary artery catheters and echocardiography. Adequate NAVA level identified by a titration procedure to breathing pattern (NAVAal), 50% NAVAal, and 200% NAVAal and adequate pressure support (PSVal, defined clinically), 50% PSVal, and 150% PSVal were implemented at constant positive end-expiratory pressure for 20 minutes each.ResultsNAVAal was 3.1 ± 1.1cmH2O/μV and PSVal was 17 ± 2 cmH20. For all NAVA levels negative esophageal pressure deflections were observed during inspiration whereas this pattern was reversed during PSVal and PSVhigh. As compared to expiration, inspiratory right ventricular outflow tract velocity time integral (surrogating stroke volume) was 103 ± 4%, 109 ± 5%, and 100 ± 4% for NAVAlow, NAVAal, and NAVAhigh and 101 ± 3%, 89 ± 6%, and 83 ± 9% for PSVlow, PSVal, and PSVhigh, respectively (p < 0.001 level-mode interaction, ANOVA). Right ventricular systolic isovolumetric pressure increased from 11.0 ± 4.6 mmHg at PSVlow to 14.0 ± 4.6 mmHg at PSVhigh but remained unchanged (11.5 ± 4.7 mmHg (NAVAlow) and 10.8 ± 4.2 mmHg (NAVAhigh), level-mode interaction p = 0.005). Both indicate progressive right ventricular outflow impedance with increasing pressure support ventilation (PSV), but no change with increasing NAVA level.ConclusionsRight ventricular performance is less impaired during NAVA compared to PSV as used in this study. Proposed mechanisms are preservation of cyclic intrathoracic pressure changes characteristic of spontaneous breathing and limitation of right-ventricular outflow impedance during inspiration, regardless of the NAVA level.Trial registrationClinicaltrials.gov Identifier: NCT00647361, registered 19 March 2008Electronic supplementary materialThe online version of this article (doi:10.1186/s13054-014-0499-8) contains supplementary material, which is available to authorized users.

Stress Attenuation Mechanism of Foam Core Sandwich Panels Subjected to Close-Range Blast Loading

A series of experiments have been conducted to investigate the stress wave attenuation mechanism and the response of sandwich panels made of steel face sheets with foam cores under blast loading in close range. Quantitative results including shock wave pressure and face sheet deflection were obtained and the deformation/failure modes of specimens were identified and discussed systematically. Results show that the face sheet deflection was reduced by adopting a higher density core, however, performance of sandwich panels in blast wave attenuation degrade. Cell collapse type of the central region of the foam core is dominated by brittle crushing under close-range blasting loading. All front face sheets produce localized failure at the focal area and global deformation in the peripheral region.

Interactions of vortices with a flexible beam with applications in fluidic energy harvesting

A cantilever piezoelectric beam immersed in a flow and subjected to naturally occurring vortices such as those formed in the wake of bluff bodies can be used to generate electrical energy harvested in fluid flows. In this paper, we present the pressure distribution and deflection of a piezoelectric beam subjected to controlled vortices. A custom designed experimental facility is set up to study the interaction of individual and multiple vortices with the beam. Vortex tori are generated by an audio speaker and travel at controlled rates over the beam. Particle image velocimetry is used to measure the 2-D flow field induced by each vortex and estimate the effect of pressure force on the beam deflection.

Offshore anchor piles under mooring forces: centrifuge modeling

Offshore anchor piles are seafloor moorings that keep the position of floating structures during a harsh environment. These piles are usually subjected to a wide range of monotonic and cyclic lateral-to-oblique pullout forces. Centrifuge tests were carried out to study the behavior of offshore anchor piles under mooring forces in saturated dense sand. The tests were carried out at different loading angles. All piles were jacked into the sand bed in-flight. The pile models were instrumented with strain gauges. Bending moment, soil pressure, and pile lateral deflection profiles are presented and discussed. It was found that there is a significant interaction between both tension and lateral loading. This interaction should be considered in the design of offshore anchor piles.

Design, Manufacture, and Testing of the Easycuff™ Pressure Measuring Syringe

A pressure measuring syringe, known as the EasyCuff™, has been designed and manufactured to provide physicians with a tool to accurately measure the pressure inside the distal cuff of endotracheal tube tubes (ETTs). The syringe, identical in size to a standard 10 cc syringe, has four components: a seal, a plunger, a barrel, and a silicone-rubber bellows (the pressure measuring component). A finite-element model of the bellows was created using ADINA™; silicone rubber bellows were then produced and shown to correlate linearly with the model to within ±5% up to a load equivalent to an internal pressure of 200 cm H2O. 20 of these bellows were then assembled into EasyCuff™ syringes and tested to assess their accuracy and repeatability. The experimental setup used a currently-available manometer, which the EasyCuff™ is designed to replace, as a reference tool. The data show that the relationship between measured pressure and bellows deflection is linear, with a correlation factor of R2 = 0.99; additionally, environmental testing showed that the EasyCuff™ is unaffected by temperature cycling between −15 °F and +170 °F.

Characterising the failure pattern of a station box of Taipei Rapid Transit System (TRTS) and its rehabilitation

The case history where flooding due to the leakage through the openings in diaphragm wall accompanied by piping in excavation bottom severely affected the construction of a station box of Taipei Rapid Transit System (TRTS) is presented. The emergency grouting adjacent to but outside the diaphragm wall was conducted following the leakage. However, injection pressure due to slow setting time of grout not only aggravated the piping but also caused the side effect deflecting the diaphragm wall toward excavation area. The severe piping quickly washed the soil into station box and the differential settling of buildings above along with propagating surface cracks forced the use of water emplacing in station to ease the piping and further ground loss; meanwhile, seal grouting and void filling grouting were undertaken to facilitate the rehabilitation of foundation construction through which the station box was opened subsequently. Based on analyzed interactive behaviour between water emplacing or injection pressure and wall deflection or brace load, the diaphragm wall and bracing system would not have functioned normally during grouting if water had not been introduced in the station. The cause of opening in the diaphragm wall is triggered by the abnormal concrete placement which can be avoided through the suggested procedure of examination. The paper discusses the insights into a review of instrument records and provides the lessons learned.

Debris transport analysis at the intermediate focus of an extreme ultraviolet light source

As extreme ultraviolet light lithography matures, critical deficits in the technology are being resolved. Research has largely focused on solving the debris issue caused by using warm (Te ∼ 30 eV) and dense (ne ∼ 1020 cm−3) plasma to create 13.5-nm light. This research has been largely focused on the mitigation of the debris between the plasma and the collector optics. The next step of debris mitigation is investigated, namely the effect of debris mitigation on the transport of undesired contaminants to the intermediate focus (IF). In order to investigate emissions from the IF, the Center for Plasma-Material Interactions at the University of Illinois at Urbana-Champaign has developed the Sn intermediate focus flux emission detector. The effects of a secondary RF-plasma, buffer gas flow rate, chamber pressure, and charged plate deflection are investigated. By increasing the chamber pressure to 10 mTorr, flowing 1000 sccm Ar buffer gas, and utilizing charged particle deflection, it is possible to reduce the measured number of post-IF species by greater than 99%. Furthermore, it is shown that typical debris mitigation techniques lead to the development of a plasma near the IF that can be detrimental to post-IF optics.

Assessment of patient–ventilator breath contribution during neurally adjusted ventilatory assist

During neurally adjusted ventilatory assist (NAVA), it is difficult to quantify the relative contribution of the patient versus the ventilator to the inspiratory tidal volume (Vt(insp)). To solve this problem, we developed an index, the "patient-ventilator breath contribution" (PVBC), using the inspiratory deflection of the diaphragmatic electrical activity (∆EAdi) and Vt(insp) during assisted and non-assisted breaths. This study evaluated the PVBC index in an experimental setup. Nine intubated and sedated rabbits were studied during repeated ramp increases of the NAVA level. One breath was non-assisted at each NAVA level. The PVBC index was evaluated during resistive loading and after acute lung injury. PVBC was calculated by relating Vt(insp)/∆EAdi of a non-assisted breath to that of the preceding assisted breath. The PVBC was compared to the relative contribution of esophageal pressure (∆Pes) to transpulmonary pressure deflections (∆P (L,dyn)). The relationship between PVBC and ∆Pes/∆P (L,dyn) was slightly curvilinear with an intercept different from zero (y=-1x (2)+1.64x+0.21) and a determination coefficient (R (2)) of 0.95. Squaring the PVBC values resulted in a near perfect linear relationship (y=1.02x+0.05) between PVBC(2) and ∆Pes/∆P (L,dyn) with an R (2) of 0.97. This study shows that Vt(insp) and EAdi can be used to predict the contribution of the inspiratory muscles versus that of the ventilator during NAVA. If clinically applicable, this could serve to quantify and standardize the adjustment of the level of assist, and hence reduce the risks of excessive ventilatory assist. Further studies are required to evaluate if this method is clinically applicable.

A new UV-curing elastomeric substrate for rapid prototyping of microfluidic devices

Rapid prototyping in the design cycle of new microfluidic devices is very important for shortening time-to-market. Researchers are facing the challenge to explore new and suitable substrates with simple and efficient microfabrication techniques. In this paper, we introduce and characterize a UV-curing elastomeric polyurethane methacrylate (PUMA) for rapid prototyping of microfluidic devices. The swelling and solubility of PUMA in different chemicals is determined. Time-dependent measurements of water contact angle show that the native PUMA is hydrophilic without surface treatment. The current monitoring method is used for measurement of the electroosmotic flow mobility in the microchannels made from PUMA. The optical, physical, thermal and mechanical properties of PUMA are evaluated. The UV-lithography and molding process is used for making micropillars and deep channel microfluidic structures integrated to the supporting base layer. Spin coating is characterized for producing different layer thicknesses of PUMA resin. A device is fabricated and tested for examining the strength of different bonding techniques such as conformal, corona treating and semi-curing of two PUMA layers in microfluidic application and the results show that the bonding strengths are comparable to that of PDMS. We also report fabrication and testing of a three-layer multi inlet/outlet microfluidic device including a very effective fluidic interconnect for application demonstration of PUMA as a promising new substrate. A simple micro-device is developed and employed for observing the pressure deflection of membrane made from PUMA as a very effective elastomeric valve in microfluidic devices.

Analysis of a typical railway turnout sleeper system using grillage beam analogy

A simplified grillage beam analogy was performed to investigate the behaviour of railway turnout sleeper system with a low value of elastic modulus on different support moduli. This study aimed at determining an optimum modulus of elasticity for an emerging technology for railway turnout application - fibre composites sleeper. The finite element simulation suggests that the changes in modulus of elasticity of sleeper, E sleeper and the sleeper support modulus, U s have a significant influence on the behaviour of turnout sleepers. The increase in U s from 10 to 40 MPa resulted in a 15% reduction in the bending moment while the increase in E sleeper from 1 GPa to 10 GPa has resulted in almost 75% increase in the bending moment. The shear forces in turnout sleepers is not sensitive to both the changes of the E sleeper and U s while the sleeper with low E sleeper tend to undergo greater settlement into the ballast. An E sleeper of 4 GPa was found optimal for an alternative fibre composite turnout sleeper provided that the U s is at least 20 MPa from the consideration of sleeper ballast pressure and maximum vertical deflection. It was established that the turnout sleeper has a maximum bending moment of 19 kN-m and a shear force of 158 kN under service conditions.

Classifying Different Types of Double Triggering Based on Airway Pressure and Flow Deflection in Mechanically Ventilated Patients

Double-triggering (DT) is a frequent type of patient-ventilator asynchrony and has potentially severe consequences, such as alveolar overdistention or the generation of intrinsic PEEP. However, the first breath of DT could be patient-triggered (DT-P), auto-triggered (DT-A), or ventilator-triggered (DT-V). To differentiate DT-P, DT-A, and DT-V using airway pressure or flow changes during the trigger-delay phase in ventilated patients. Fourteen mechanically ventilated patients with DT were included. All patients were on flow-triggered ventilation modes and received either continuous mandatory ventilation or pressure support ventilation. Breaths in which the first breath was associated with an esophageal pressure drop of > 1 cm H(2)O were categorized as DT-P. Breaths in which the first breath occurred at the ventilator set cycle were categorized as DT-V. Breaths in which the first breath occurred earlier than the ventilator set cycle without esophageal pressure drop were categorized as DT-A. The pressure drop and flow change at 0.13 s (PD(0.13) and F(0.13), respectively) in the trigger-delay phase were calculated from the nadir. There were 507 double-triggered breaths: 271 DT-V (53%), 50 DT-A (10%), and 186 DT-P (37%). The PD(0.13) for DT-V, DT-A, and DT-P were 0.16 ± 0.12 cm H(2)O, 0.25 ± 0.17 cm H(2)O, and 1.34 ± 0.67 cm H(2)O, respectively. The F(0.13) for DT-V, DT-A, and DT-P were 2.11 ± 2.31 L/min, 2.64 ± 2.07 L/min, and 16.51 ± 8.02 L/min, respectively. The best discriminatory criteria for differentiating DT-P from DT-V and DT-A, based on the Youden index (sensitivity + specificity - 1) was PD(0.13) ≥ 0.49 cm H(2)O, which had a Youden index of 95%. DT-P can be distinguished from DT-V and DT-A by using airway pressure deflections in the trigger-delay phase.

A coupled approach for rolling contact fatigue cracks in the hydrodynamic lubrication regime: The importance of fluid/solid interactions

This article presents a novel approach for modelling rolling contact fatigue cracks in the presence of lubricants. The proposed formulation captures the interaction between fluid pressure and solid deflections both at the contact interface and along the crack faces using a fully coupled finite volume/boundary element solver. This sheds light on the mechanisms which govern crack propagation in various loading conditions and geometrical configurations. It is shown that by linking the fluid behaviour and the elastic deflections within the crack to the film formed at the contact interface it is possible to overcome one of the main limitations of classical models available in the literature, which consists of having to prescribe pressure and/or pressure gradient at the crack mouth during the each loading cycle. The application of linear elastic fracture mechanics principles for the determination of crack stress intensity factors suggests that the approach developed by the authors produces a more realistic characterisation of the crack tip behaviour and it is capable of producing an improved estimate of crack propagation rates. Implications of these findings for the development of rolling contact fatigue lifing tools and potential extensions of the technique are also discussed.

Laser Entrance Hole Window Burst and Pressure Deflections at Cryogenic Temperature

Laser entrance hole (LEH) windows for hohlraums must have minimal thickness yet must contain low-temperature tamping gas in a reproducible envelope at 52 kPa. Given the high cost of a window failure, it is important to understand variability in the finished windows. Polyimide LEH window pressure deflection profiles were measured at 18 K. The shape and magnitude of pressure deflections of LEH windows were well described using thin film elastic mechanics. Subsequently, 24 windows with 3.9-mm apertures were selected from several production lots to measure reproducibility. The windows were cooled to 18 K, and their leak rates, deflections to 52 kPa, and burst pressures were measured. The mean window deflection at 18 K was 260 μm, with a standard deviation of 20 μm. Variability in window deflections was well described by an anisotropic initial strain model. Window burst pressure was found to obey first-order Weibull statistics. The predicted failure rate for the use conditions was extrapolated to be <0.1%.

Dynamics of thin film flow on flexible substrate

The dynamics of continuous thin film flow over flexible substrate is explored. Lubrication theory is employed to model the flow, resulting in a system of coupled equations for film thickness, pressure and substrate deflection which are solved numerically subject to appropriate boundary conditions. This is achieved accurately and efficiently using an automatic time and space adaptive multigrid strategy. Of particular interest are the dynamics that occur as a consequence of pulsing the inlet flow over substrate that is either uniformly flexible or contains localised regions of uniform and varying flexibility. Results are presented for the free-surface disturbances and corresponding substrate deflections that arise, with conclusions drawn concerning how substrate flexibility affects the practical issue of free-surface planarisation.

High speed wafer scale bulge testing for the determination of thin film mechanical properties

A wafer scale bulge testing system has been constructed to study the mechanical properties of thin films and microstructures. The custom built test stage was coupled with a pressure regulation system and optical profilometer which gives high accuracy three-dimensional topographic images collected on the time scale of seconds. Membrane deflection measurements can be made on the wafer scale (50-150 mm) with up to nanometer-scale vertical resolution. Gauge pressures up to 689 kPa (100 psi) are controlled using an electronic regulator with and accuracy of approximately 0.344 kPa (0.05 psi). Initial testing was performed on square diaphragms 350, 550, and 1200 microm in width comprised of 720+/-10 nm thick low pressure chemical vapor deposited silicon nitride with approximately 20 nm of e-beam evaporated aluminum. These initial experiments were focused on measuring the system limitations and used to determine what range of deflections and pressures can be accurately measured and controlled. Gauge pressures from 0 to approximately 8.3 kPa (1.2 psi) were initially applied to the bottom side of the diaphragms and their deflection was subsequently measured. The overall pressure resolution of the system is good (approximately 350 Pa) but small fluctuations existed at pressures below 5 kPa leading to a larger standard deviation between deflection measurements. Analytical calculations and computed finite element analysis deflections closely matched those empirically measured. Using an analytical solution that relates pressure deflection data for the square diaphragms the Young's modulus was estimated for the films assuming a Poisson's ratio of v=0.25. Calculations to determine Young's modulus for the smaller diaphragms proved difficult because the pressure deflection relationship remained in the linear regime over the tested pressure range. Hence, the calculations result in large error when used to estimate the Young's modulus for the smaller membranes. The deflection measurements of three 1200 x 1200 microm(2) Si(3)N(4-x) membranes were taken at increased pressures (>25 kPa) to increase nonlinearity and better determine Young's modulus. This pressure-deflection data were fit to an analytical solution and Young's modulus estimated to be 257+/-3 GPa, close to those previously reported in literature.